During the Carboniferous period, huge forests of the primitive plants spread through the low-lying
swamplands. These swamps housed a lot of strange animals, fueled by the excessive amounts of oxygen
the trees produced. Then, towards the end of the Carboniferous, the climate became drier and
these forests fragmented. But some of the swamp forests remained well into the Permian, and life
in the swamplands continued. But not everything living in these new swamps was so familiar.
It is the early Permian, and terrestrial ecosystems have come a long way since
the first creatures crawled onto land. But many primitive relics of earlier times remained. A lot
of Permian plants were members of ancient lineages that originated before the evolution of seeds,
so they still use spores to reproduce like ferns do today. Ferns themselves were common in the
forests, with some of them growing into trees that were 30 feet high. While ferns survive in large
numbers to this day, many other primitive plant groups, like the lycopsids and equisetopsids,
are much less common in modern times, consisting of only a few small varieties. Their decline had
already begun in the Carboniferous, but you could still find 100-foot-tall equisetopsids
towering above the rest of the forest and these Euramerican swamps of the early Permian.
Nevertheless, these plants were disadvantaged by their reliance on spores to reproduce. Since
spores dry out easily, plants that produce them are restricted to wetter areas. But not
all Permian plants were so primitive. Many early seed producing plants were present,
including some of the earliest conifers, cycads, and other gymnosperms. Their use
of seeds to protect their embryos meant that they could colonize drier environments than
other plants could, but they were becoming more and more common in the swamps as well.
The atmospheric oxygen levels had not changed much since the Carboniferous. They were still
at about 35%: nearly twice the modern level. And just like in the Carboniferous, this meant that
land arthropods could grow enormous, since their primitive respiratory system doesn't allow them
to grow large if there isn't enough oxygen in the air. The largest terrestrial arthropod, the
ten-foot Arthropleura, still roamed the swamps, and the skies were still ruled by giant relatives
of the dragonflies. Meganeuropsis permiana, the largest known insect of all time, was one
of them. It had a wingspan of nearly three feet across. Although these giants ruled the skies,
the roach-like "blattopterans", among the most abundant insects of the time, inhabited the leaf
litter, and ancient paleodictyopteran lineages could still be found feeding on the plants. Among
the arachnids there was the usual assortment of spiders, scorpions, whip scorpions, and the
extinct trigonotarbids, all of which had already been established for a long time. By now, bivalves
had spread to freshwater, including the waters permeating the swamps. Among the gastropods,
snails had lived in marine environments since the early days of the Paleozoic, but starting in the
Carboniferous, they also started to invade fresh water, and by the time the Permian rolled around,
terrestrial snails had colonized the land, although these snails were likely unrelated to
today's land snails. Higher up on the food chain, freshwater sharks were still present. Older fish
groups like the "acanthodians" and sarcopterygians were much rarer than they used to be. But one
group of sarcopterygians, the tetrapods, was doing well. Most tetrapods at this time belonged to more
primitive groups that still laid their eggs in water. Today, the only living tetrapods that do
this are modern amphibians, but in the Permian you can still find a huge variety of these creatures
that have since been lost to time. Unlike modern amphibians, they had not yet lost their scales,
so they couldn't breathe through their skin, but a lot of them probably possessed gills in
addition to their lungs. Creatures like these had been hit hard by the shrinking of the swamplands
at the end of the Carboniferous, but many of these groups managed to stick it out. Some of them were
closer to modern groups, but some were far more basal than any living tetrapods. Scientists seem
to have a hard time agreeing on where certain organisms fit into this family tree. Regardless,
these groups contain multitudes of strange forms, from insectivores to terrestrial herbivores to
legless swimmers to large ambush predators like the Eryopids, which could grow up to 10 feet long.
The eryopids belonged to the temnospondyls, which is the group that most scientists seem
to agree evolved into modern amphibians: the lissamphibians. One temnospondyl from this time,
Gerobatrachus hottoni, is thought by some to be the earliest known lissamphibian. On the other end
of the tetrapod family tree, the reptiliomorphs were still common as well. This group is thought
to contain many of the lepospondyls, like the famous Diplocaulus. It also contains several
more terrestrial groups, like the diadectomorphs. Among the diadectomorphs were aquatic carnivores
like Limnoscelis, but this group also included the only primitive tetrapods that ever evolved
to be herbivorous, such as Diadectes itself. But in the last 20 million years, a new kind of
reptiliomorph has joined these ancient ecosystems: one that you'd be hard-pressed to find in the
Carboniferous forests. You may remember that the Carboniferous period saw the dawn of the amniotes:
tetrapods with watertight skin and, crucially, eggs with watertight shells that can be laid
on land instead of in the water like amphibians. All fully terrestrial vertebrates, from reptiles
to birds to mammals, are members of this group. Before the end of the Carboniferous, Amniota had
split into two main groups: the sauropsids and the synapsids. While there are a few features of
the skull that distinguished the two groups, both of them generally had the same primitive amniote
look at this point in their evolution. One obvious difference between the synapsids and sauropsids,
though, is that the synapsids got big. By the end of the Carboniferous, there were 10-foot synapsid
carnivores and herbivores prowling the swamps, and these new groups continued into the Permian,
evolving into many shapes and sizes. They represented the Earth's first terrestrial
megafauna. The land was dominated by these strange creatures, and the swamps were no
exception. However, at this time their ecology was very different from large land animals of today.
Large herbivores were rare, and rather than a simple plant-to-herbivore-to-carnivore food chain,
these food chains were more similar to aquatic ones: a long series of predators being eaten by
larger and larger predators. There was still a ways to go before more modern food chains
evolved. Not all swamps in the early Permian were like those of Euramerica. Different regions
had different mixtures of these plant groups, and some fared better than they did in these
equatorial swamps. Towards the Siberian end of Pangaea, the giant primitive seed
plant Cordaites was more common. Meanwhile, in the southern, colder parts of Pangaea,
there were swamps dominated by early conifers, ginkgos, and a seed plant called Glossopteris,
one of the most successful plants of all time. And in the east, more primitive, Carboniferous
varieties of plants found refuge on the islands that would one day become China. These islands
were some of the few places where you could still find the bizarre lycopsid trees in abundance.
Many millions of years later, when the other wetlands would succumb to the drier climate,
these islands would serve as the last refuge of the primitive forests that once spanned the globe.